Formulators often wish to provide liquid detergent compositions in thickened form. Aesthetically, thickness can connote richness or strength of the compositions. In some instances, the formulator may wish to suspend solid materials such as abrasives or particulate bleaches in the liquid compositions. A wide variety of thickeners have been developed for such uses.
Liquid cleaning compositions which are especially designed for direct application to hard surfaces are often thickened to provide ease-of-use on vertical surfaces such as bathroom shower walls, toilets and bathtub walls. The cleaning of such environmental surfaces can be problematic, inasmuch as calcareous deposits, commonly known as "lime scale", are often formed thereon by water hardness. In order to provide good lime scale removal, it is highly preferred to formulate cleaning compositions at acidic pH's, often at pH's in the range of 2-3.
Unfortunately, it can be difficult to thicken liquid cleaning compositions at acidic pH's. Conventional thickening polymers often do not exhibit Newtonian flow properties under such circumstances and are not optimal for such use. Monomeric thickeners which may exhibit Newtonian flow properties at higher pH's do not function well in the acid range.
It has now been determined that certain N-hydroxyalkyl succinimides provide thickened aqueous cleaning compositions. These compositions are stable and exhibit substantially Newtonian flow properties even at low pH. These compositions can be employed in any circumstance where thickened liquid cleaning compositions are desirable, but can be formulated to be especially useful for removing lime scale from household environmental surfaces. The succinimide compounds used herein are also substantially less expensive than other thickeners known in the art.